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Abstract

We propose and demonstrate a novel technique for measuring the distribution of
the reflectivity along an optical fiber transmission line. Unlike the
conventional optical time-domain reflectometer (OTDR), the proposed technique
utilizes the data-modulated transmitter itself instead of the optical
short-pulse source, and monitors the distribution of the back-reflected light by
calculating the cross-correlation of the transmitted and back-reflected signals.
In this paper, we describe the operating principle of the proposed technique and
discuss its potential limitation on the dynamic range. We also show that this
limitation can be mitigated by using the discrete-component elimination
algorithm. In addition, we experimentally demonstrate that the proposed
technique can be used for the in-service monitoring of the transmission fibers
in a wavelength-division multiplexed passive optical network (WDM PON).

K. Tanaka, H. Izumita, N. Tomita, and Y. Inoue, “In-service individual line
monitoring and a method for compensating for the temperature-dependent
channel drift of a WDM-PON containing an AWGR using a 1.6 mm tunable
OTDR,” in Proceedings of European Conference on Optical Communication, 3, paper 448, pp. 295–298 (1997).

Inoue, Y.

K. Tanaka, H. Izumita, N. Tomita, and Y. Inoue, “In-service individual line
monitoring and a method for compensating for the temperature-dependent
channel drift of a WDM-PON containing an AWGR using a 1.6 mm tunable
OTDR,” in Proceedings of European Conference on Optical Communication, 3, paper 448, pp. 295–298 (1997).

Izumita, H.

K. Tanaka, H. Izumita, N. Tomita, and Y. Inoue, “In-service individual line
monitoring and a method for compensating for the temperature-dependent
channel drift of a WDM-PON containing an AWGR using a 1.6 mm tunable
OTDR,” in Proceedings of European Conference on Optical Communication, 3, paper 448, pp. 295–298 (1997).

Takeuchi, N.

Tanaka, K.

K. Tanaka, H. Izumita, N. Tomita, and Y. Inoue, “In-service individual line
monitoring and a method for compensating for the temperature-dependent
channel drift of a WDM-PON containing an AWGR using a 1.6 mm tunable
OTDR,” in Proceedings of European Conference on Optical Communication, 3, paper 448, pp. 295–298 (1997).

K. Tanaka, H. Izumita, N. Tomita, and Y. Inoue, “In-service individual line
monitoring and a method for compensating for the temperature-dependent
channel drift of a WDM-PON containing an AWGR using a 1.6 mm tunable
OTDR,” in Proceedings of European Conference on Optical Communication, 3, paper 448, pp. 295–298 (1997).

K. Tanaka, H. Izumita, N. Tomita, and Y. Inoue, “In-service individual line
monitoring and a method for compensating for the temperature-dependent
channel drift of a WDM-PON containing an AWGR using a 1.6 mm tunable
OTDR,” in Proceedings of European Conference on Optical Communication, 3, paper 448, pp. 295–298 (1997).

Figures (6)

(a). The autocorrelation function of the reference signal. The dashed
curve shows the autocorrelation function calculated by using the
ensemble average with infinite averaging time. The solid curve shows the
autocorrelation function with a finite length of the sampled data.
(N=4096). The inset shows the same trace plotted in
log scale. (b) The background noise suppression ratio (BNSR) calculated
as a function of the number of sampling points. Dots and open circles
show the BNSR simulated for cases when
fc/fs=0.1
and 0.3, respectively.

Limitation on the dynamic range due to the BNSR and its improvement by
the discrete component elimination algorithm. (a) Simulation model. (b)
The cross-correlation trace. (c) The cross-correlation trace after
applying the discrete component elimination algorithm to (b).

(a). Cross-correlation trace when a 2.2-km fiber with open end was measured.
(b) Cross-correlation trace when the discrete component elimination
algorithm was applied to (a). The red dotted lines show the root-mean square
of the background noise, and the BNSR was defined by the ratio of the peak
to this background noise level. (c) The BNSR measured as a function of the
number of sampling points. Open circles and dots show the BNSR measured with
and without the discrete component elimination algorithm. The dashed line
shows the theoretical BNSR calculated by using Eq. (7).

In-service monitoring of the WDM PON system. (a) Without averaging. (b) With
averaging of 400 traces. The dashed line shows the root mean square of the
background noise. (c) Cross-correlation trace when a fiber break with a
small reflection of -39.2 dB was intentionally made just before the ONU.